Method for preparing silica filled elastomeric compositions

Abstract

A process for preparing a cross-linked blend comprising a) mixing a copolymer of a C 4 to C 7 isoolefin and a para-alkylstyrene with silica, b) separately mixing a general purpose rubber with silica, wherein one or more silane coupling agents is mixed with at least one of the silica/copolymer or silica/general purpose rubber blends, and c) mixing the silica/copolymer blend with the silica/general purpose rubber blend. Typical silane coupling agents include bis(3-triethoxysilylpropyl) tetrasulfide, 3-thiocyanatopropyl-triethoxy silane, 3-mercaptopropyl-trimethoxy silane, and one embodiment of the copolymer is a terpolymer of isobutylene, para-methylstyrene, and bromo-para-methylstyrene.

We claim:  
     
         1 . A process for preparing a blend comprising: 
 a) mixing a copolymer of a C 4  to C 7  isoolefin and a para-alkylstyrene with silica;    b) separately mixing a general purpose rubber with silica, wherein one or more silane coupling agents is mixed with at least one of the silica/copolymer or silica/general purpose rubber mixtures; and    c) mixing the silica/copolymer mixture with the silica/general purpose rubber mixture to form the blend.    
     
     
         2 . The process of  claim 1 , wherein the general purpose rubber is selected from the group consisting of natural rubber, polybutadiene, polyisoprene, styrene-butadiene rubber, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, isoprene-butadiene rubber, neoprene, polychloroprene, butyl rubber, nitrile rubber and blends thereof.  
     
     
         3 . The process of  claim 2 , wherein the general purpose rubber is selected from the group consisting of natural rubber, polybutadiene, polyisoprene, styrene-butadiene rubber, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, isoprene-butadiene rubber and blends thereof.  
     
     
         4 . The process of  claim 3 , wherein the general purpose rubber is selected from the group consisting of natural rubber, polybutadiene, styrene-butadiene rubber and blends thereof.  
     
     
         5 . The process of  claim 1 , wherein the C 4  to C 7  isoolefin is isobutylene.  
     
     
         6 . The process of  claim 5 , wherein the para-alkylstyrene is para-methylstyrene.  
     
     
         7 . The process of  claim 1 , wherein the copolymer is a terpolymer of isobutylene, para-methylstyrene and bromo para-methylstyrene.  
     
     
         8 . The process of  claim 1 , wherein the blend is colorable.  
     
     
         9 . The process of  claim 1 , wherein the blend is substantially free of carbon black and antioxidant.  
     
     
         10 . The process of  claim 1 , wherein the blend comprises: 
 a) from 10 to 100 phr of the copolymer of a C 4  to C 7  isoolefin and a para-alkylstyrene;    b) from 10 to 100 phr of the general purpose rubber;    c) from 10 to 100 phr of the silica; and    d) from 0.1 to 20 wt % of the coupling agent, based on the weight of the blend.    
     
     
         11 . The process of  claim 10 , wherein the general purpose rubber is selected from the group consisting of natural rubber, polybutadiene, polyisoprene, styrene-butadiene rubber, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, isoprene-butadiene rubber, neoprene, polychloroprene, butyl rubber, nitrile rubber and blends thereof.  
     
     
         12 . The process of  claim 10 , wherein the copolymer is a terpolymer of isobutylene, para-methylstyrene and bromo para-methylstyrene.  
     
     
         13 . The process of  claim 12 , wherein the blend comprises from 20 to 100 phr of a terpolymer of isobutylene, para-methylstyrene and bromo para-methylstyrene.  
     
     
         14 . The process of  claim 10  wherein the silica is precipitated silica.  
     
     
         15 . The process of  claim 14 , wherein the blend comprises from 30 to 80 phr of precipitated silica.  
     
     
         16 . The process of  claim 10 , wherein the coupling agent is an organosilane coupling agent.  
     
     
         17 . The process of  claim 16 , wherein the blend comprises from 2 to 15 wt % of an organosilane-coupling agent, based on the weight of the blend.  
     
     
         18 . The process of  claim 1 , wherein the coupling agent is an organosilane coupling agent selected from the group consisting of bis-(3(triethoxysilyl)-propyl)-tetrasulfane, gamma-mercaptopropyltrimethoxysilane, 3-thiocyanatopropyl-triethoxy silane and blends thereof.  
     
     
         19 . The blend produced by the process of  claim 1 .  
     
     
         20 . A process for preparing a blend comprising: 
 a) mixing a general purpose rubber with silica and one or more coupling agents to form a silica/general purpose rubber mixture; and    b) mixing the silica/general purpose rubber mixture with a copolymer of a C 4  to C 7  isoolefin and a para-alkylstyrene to form the blend.    
     
     
         21 . The process of  claim 20 , wherein the amount of time the silica/general purpose rubber blend is mixed with the copolymer of a C 4  to C 7  isoolefin and a para-alkylstyrene is varied to control the silica dispersion between the general purpose rubber and the copolymer in the elastomeric blend.  
     
     
         22 . The process of  claim 20 , wherein the general purpose rubber is selected from the group consisting of natural rubber, polybutadiene, polyisoprene, styrene-butadiene rubber, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, isoprene-butadiene rubber, neoprene, polychloroprene, butyl rubber, nitrile rubber and blends thereof.  
     
     
         23 . The process of  claim 22 , wherein the general purpose rubber is selected from the group consisting of natural rubber, polybutadiene, polyisoprene, styrene-butadiene rubber, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, isoprene-butadiene rubber and blends thereof.  
     
     
         24 . The process of  claim 23 , wherein the general purpose rubber is selected from the group consisting of natural rubber, polybutadiene, styrene-butadiene rubber and blends thereof.  
     
     
         25 . The process of  claim 20 , wherein the C 4  to C 7  isoolefin is isobutylene.  
     
     
         26 . The process of  claim 25 , wherein the para-alkylstyrene is para-methylstyrene.  
     
     
         27 . The process of  claim 20 , wherein the copolymer is a terpolymer of isobutylene, para-methylstyrene and bromo para-methylstyrene.  
     
     
         28 . The process of  claim 20 , wherein the blend is colorable.  
     
     
         29 . The process of  claim 20 , wherein the blend is substantially free of carbon black and antioxidant.  
     
     
         30 . The elastomeric blend produced by the process of  claim 20 .  
     
     
         31 . The process of  claim 1 , further comprising adding sulfur in step b), step c), or both.  
     
     
         32 . A process for preparing a blend comprising: 
 a) mixing a copolymer of a C 4  to C 7  isoolefin and a para-alkylstyrene with silica and one or more coupling agents to form a silica/copolymer mixture;    b) separately mixing a general purpose rubber with silica and one or more coupling agents to form a silica/general purpose rubber mixture; and    c) mixing the silica/copolymer mixture with the silica/general purpose rubber mixture to form the blend.    
     
     
         33 . The process of  claim 32 , wherein the general purpose rubber is selected from the group consisting of natural rubber, polybutadiene, polyisoprene, styrene-butadiene rubber, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, isoprene-butadiene rubber, neoprene, polychloroprene, butyl rubber, nitrile rubber and blends thereof.  
     
     
         34 . The process of  claim 33 , wherein the general purpose rubber is selected from the group consisting of natural rubber, polybutadiene, polyisoprene, styrene-butadiene rubber, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, isoprene-butadiene rubber and blends thereof.  
     
     
         35 . The process of  claim 34 , wherein the general purpose rubber is selected from the group consisting of natural rubber, polybutadiene, styrene-butadiene rubber and blends thereof.  
     
     
         36 . The process of  claim 32 , wherein the C 4  to C 7  isoolefin is isobutylene.  
     
     
         37 . The process of  claim 36 , wherein the para-alkylstyrene is para-methylstyrene.  
     
     
         38 . The process of  claim 32 , wherein the copolymer is a terpolymer of isobutylene, para-methylstyrene and bromo para-methylstyrene.  
     
     
         39 . The process of  claim 32 , wherein the blend is colorable.  
     
     
         40 . The process of  claim 32 , wherein the blend is substantially free of carbon black and antioxidant.  
     
     
         41 . A blend comprising: 
 an isoolefin/para-alkylstyrene copolymer, the isoolefin having between 4 and 7 carbon atoms and the copolymer containing from about 0.5 wt % to about 20 wt % by weight para-alkylstyrene, and wherein from about 0.2 mole % to about 3 mole % of the methyl groups present on the benzene ring of the para-alkylstyrene contain a halogen atom;    a general purpose rubber selected from the group consisting of polybutadiene, polyisoprene, styrene-butadiene rubber, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, isoprene-butadiene rubber, neoprene, polychloroprene, butyl rubber and nitrile rubber as well as mixtures thereof;    a silica filler; and    at least one silane coupling agent of the following structure:                           wherein R 1  can be a vinyl, sulfur, amine, alkylthiol, alkylamine, alkylsilane, alkoxysilane, methacrylate, nitroso, or halogen group; R 2  through R 4  can be the same or different, and can be an alkyl, aryl alkyl group, or a phenyl group, and n is an integer from 1 to 10.    
     
     
         42 . The blend of  claim 41 , wherein the C 4  to C 7  isoolefin is isobutylene.  
     
     
         43 . The blend of  claim 42 , wherein the silane coupling agent is selected from the group consisting of bis(3-triethoxysilylpropyl) tetrasulfide, 3-thiocyanatopropyl-triethoxy silane, 3-mercaptopropyl-trimethoxy silane, vinyl triethoxysilane, vinyl-tris-(beta-methoxyethoxy)silane, methacryloylpropyltrimethoxysilane, gamma-amino-propyl triethoxysilane, gamma-mercaptopropyltrimethoxysilane bis(2-triethoxysilyl-ethyl) tetrasulfide, bis(3-trimethoxysilyl-propyl) tetrasulfide, bis(2-trimethoxysilyl-ethyl) tetrasulfide, 3-mercaptopropyl-triethoxy silane, 2-mercaptopropyl-trimethoxy silane, 2-mercaptopropyl-triethoxy silane, 3-nitropropyl-trimethoxysilane, 3-nitropropyl-triethoxysilane, 3-chloropropyl-trimethoxysilane, 3-chloropropyl-triethoxysilane, 2-chloropropyl-trimethoxysilane, 2-chloropropyl-triethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl-benzothiazole tetrasulfide, 3-triethoxysilylpropyl-benzothiazole tetrasulfide, 3-trimethoxysilylpropyl-methacrylate monosulfide, 3-trimethoxysilylpropyl-methacrylate monosulfide, and mixtures thereof.